At present, many of the world's nations are seeking access to the outer space environment. For some, the issue is national security, and for others, economic growth. While the United States has made access possible through development of the Space Shuttle, our leadership is increasingly challenged. Soviet shuttle and heavy lift launcher development, the French Ariane launch vehicle and Hermes "space plane", and efforts of other advanced-technology countries sharpen the intensity of competition in the near term. In parallel, the United States faces increasing budget deficits and a widening gap in balance of trade. It is with these realities in mind that the President and Congress have advanced the concept of United States Commercialization of Space--an endeavor to involve American industry in the development and utilization of the space environment. Private enterprise has been challenged to take a leading role in the nation's civilian space activities, to bring entrepreneurial inventiveness to bear in a marketplace of seemingly limitless potential.
While past governmental efforts in space have been primarily performance driven, it is now appropriate that a more cost-conscious path be pursued. Commercial programs require commonality and compatibility of equipment and systems, and lowered production costs to make them economically feasible. The proper mix of performance technology and cost-efficient application will insure America's sustained leadership in the exploration of space and provide the American people with more effective means of carrying out activities in that medium.
One area in which the foregoing inventiveness and leadership is required is the design and development of space enclosing structures, such as those commonly known as space stations. There have been a variety of designs proposed for the deployment of space stations. The earliest designs centered on the idea that the entire space station should be lifted into earth orbit in one launch. Such a space station is described, for example, in U.S. Pat. No. 3,169,725. Working within the restriction of only one launch, however, places severe size and weight limitations on the space station. An actual example of such a space station is Skylab. The early designs had a major drawback, in that they did not have the capability for expansion.
Attempts have been made to design single-launch space stations that are collapsible. One such design is shown in U.S. Pat. No. 3,169,725. The space station design contemplated therein folds up and is projected into orbit in its folded position. Upon reaching orbit, parts of the station inflate, and it unfolds to full deployment. Such a design would appear to be limited in its capabilities to undergo future expansion. Also, maintenance or replacement of modules would be quite difficult, especially if part of the station were inflatable.
Another single-launch design is shown in U.S. Pat. No. 3,332,640. As with other single-launch designs, this one suffers from the lack of ability to undergo future expansion, and the difficulty of maintenance and replacement of defective modules.
A more recent attempt (U.S. Pat. No. 4,057,207) has been the design of a space station comprised of modular components capable of being delivered into orbit by the Space Shuttle. The geometry of this modularly constructed space station calls for the modules to be truncated icosahedra, the truncations occurring where up to three pentangular pyramids about nonadjacent verticies have been removed from each icosahedron. Although the geometry of a truncated icosahedron allows limited flexibility for the ultimate shape or design of the space station, it would apparently create the problem of providing irregular interior surfaces within the space station since an icosahedron has twenty faces. Further, the modules do not appear to be flexible in their uses; rather, they are simply parts of a unitary space station design concept.
Structures intended for sustained occupation by humans in space are in essence pressure vessels, and their design requires a high degree of pressure-containing and supporting capability in order to avoid a potentially catastrophic loss of pressure in space. In the past, pressure vessels which have required rigid structural supporting frameworks have typically provided such frameworks on the interior of the vessels due to external fluid flow considerations. Examples of pressure vessels having such internalized supporting frameworks include submarines, airplanes, and launch vehicles or rockets. While such pressure vessels are suitable for their intended purposes, their internalized framework designs are unnecessary for habitable space structures, since such fluid flow considerations play a lesser role in space and since such internal frameworks would occupy valuable space inside the pressure vessel which can be better utilized for other purposes.